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Law 792-GRD: Legal Research and Writing for LLMs: Unit 1: Overview


This page will provide you with an overview of legal information and introduce you to the sources of American law.

At the end of this lesson you should be able to:

  • Name the four sources of American law
  • Articulate the difference between a primary and secondary source
  • Explain the use of a primary source of law.
  • Explain the use of a legal secondary source

What is Legal Research?

Wscales of justicehile there is no one standardized definition, two legal research scholars have defined legal research as "the process of identifying and retrieving information necessary to support legal decision-making. In its broadest sense, legal research includes each step of a course of action that begins with an analysis of the facts of a problem and concludes with the application and communication of the results of the investigation."

An initial step in developing legal research expertise is to develop an understanding of the types of materials that constitute "the law," and of the relationships between these materials. When researching a legal issue, it is often necessary to explore statutes (legislative enactments), cases (opinions of the judiciary), and/or regulatory materials (administrative agency regulations and decisions). All these types of materials are considered "primary sources."Additionally, most resources look at at least one supplementary resources, called "secondary sources," to aid their research process.

A common, and sometimes significant, challenge for a novice researcher is to gain a perspective on how such sources may apply to a particular subject matter and how they relate to each other. Typically a researcher will need to consult multiple sources and utilize different techniques for each type of resource. To further complicate the matter, a given problem may require a researcher to consult relevant materials may on any or all of the federal, state, or local levels.

With all this in mind it is easy to see why the structures, terminology, resources, and vocabulary are an essential starting point for anyone looking to learn about legal information.

**Quoted from J. Myron Jacobstein and Roy M. Mersky, Fundamentals of Legal Research, 8th ed. (Foundation Press, 2002) p. 1.

Mandatory and Persuasive Authority: A diagram

Circle with three quadrants - Top left:  PRIMARY SOURCES - Mandatory - Statutes, cases or regulations that are binding on the court in your jurisdiction are mandatory authority and must be acknowledged.  Top right: PRIMARY SOURCES - Persuasive - Primary law which has the same or similar facts, but is from another jurisdiction can be used to persuade a court in your jurisdiction. Bottom half - SECONDARY SOURCES - Persuasive: Because secondary sources are not law, they are never binding on a court.  While these sources are cited less often for their persuasive value, secondary sources are excellent--and necessary tools.

Additional Resources

Legal Research in a Nutshell, Ch. 1, pp. 1-14

Outline of American Law

When most people think of "the law" they think of those laws that are passed by the legislature. In reality the American legal system is a complex interplay of different types of law coming together to create a complete legal framework. These types of law typically follow the structure of American government, with laws being created by the legislative, judicial, and executive branch. Understanding each of these pieces, their role, and how they work together, is essential for legal research.

In the United States the four sources of law are:

  1. Constitutions: establish the form of government and enumerate its powers, as well as the rights and liberties of its citizens. In the United States constitutions are the highest legal authority at both the state and federal level.‚Äč
  2. Statutory Law (legislation): laws passed by an elected legislative body, such as the United States Congress or the Illinois General Assembly. Legislation is generally prospective in nature, time-sensitive, and organized by topic into codes.
  3. Case Law (court opinions): is created by the courts through the assembled, published appellate decisions of a jurisdiction and is binding law on the lower courts in that jurisdiction. Courts only make law on the cases brought before them. Thus, case law is reactive in nature, made in response to a dispute, and restricted to the boundaries of that dispute.
  4. Administrative Law: decisions, rules, and regulations made by the constitutional offices and administrative agencies of the executive branch. When authorized by enabling legislation, agencies promulgate rules that specify how they will carry out the law. These rules, or regulations, are collected into a topical code, similar to legislation.

Chart showing Government at top with three branches below: executive, Judicial, and Legislative. Chart shows Administrative law stemming from executive branch, statutory law stemming from legislative branch, and case law stemming from judicial branch.

Primary v. Secondary Sources: what is the difference?

When discussing legal resources it is important to know the difference between primary and secondary legal materials.

Primary sources are those resources which are the law itself. That means a primary source would be one of the four sources listed above. Lawyers use primary authority to determine what the law says about a given matter. Identifying and aggregating these materials in order to solve legal problems is what legal research is all about.

Primary sources can be persuasive or mandatory. Mandatory authority is the term used for constitutions, cases, statutes, or regulations the court must follow. A primary material is mandatory when it is binding in a given jurisdiction. For legislative and administrative materials this is often easy to figure out: Illinois statutes are binding in Illinois. Making a determination as to whether a case is mandatory takes a bit more skill. Stated as a simple rule the concept is lower courts are required to follow decisions from higher courts in the same jurisdiction.

Primary Sources can also be persuasive authority. The term persuasive authority refers to any material the court may choose to follow or consider, but which the court does not have to adhere to when making its determination. Thus, primary law from another jurisdiction or a lower court may be used as persuasive authority.

Secondary resources are those materials which analyze, editorialize, summarize, or comment on the law. These materials do not have the force of law, but can be very helpful to legal researchers. While these materials are not usually used to support arguments in the way primary materials are, they can be cited for persuasive value. More importantly, these materials can help legal researchers understand the area of law in which they are researching and even connect them to valuable primary sources.

Secondary sources are always persuasive and rarely cited to the court.

When conducting legal research it is important to be mindful of the differences between secondary and primary materials. This concept will be discussed further in other units.